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Effects of Ga substitutions in R2Al1-xGax (R = Gd, Er) alloys have been studied. Gd2Al1-xGax (x ≤ 0.2) and Er2Al1-yGay (y ≤ 0.3) alloys are found to be crystallized in Co2Si-type orthorhombic structure. With increased Ga substitution for Al, the phase transition temperature is gradually increased. For the field change of 7 T, the maximum of entropy change (-ΔSM) is increased to 14.8 J/kgK and 11.2 J/kgK in Gd2Al0.8Ga0.2 and Er2Al0.7Ga0.3 alloys compared with 11.4 J/kgK and 8.3 J/kgK of Gd2Al and Er2Al alloys. And the relative cooling power is nearly doubled to 699.6 J/kg in Gd2Al0.8Ga0.2 alloy. As increasing Ga substitution, the critical magnetic field for the transition is decreased in Gd2Al1-xGax (x ≤ 0.2) alloys, and the magnetization is increased in Er2Al1-yGay (y ≤ 0.3) alloys. The considerable ΔSM implies that those materials are promising candidates for magnetic cooling.

The effects of Fe substitution for Ti on the structural and magnetic properties of the (Ti1-xFex)3AlC2(x = 0, 0.025, 0.05, 0.075) MAX phases have been studied. The Fe substitution leads into the expansion along c-axis but shrinkage within ab-plane of the hexagonal unit cell and also the ferromagnetic state at low temperature. The Curie temperature is increased with more Fe substitution. After exfoliation and delamination, their (Ti1-xFex)3C2Tδ 2D MXenes counterparts are obtained with paramagnetic state, which is due to the broken exchange coupling along c-axis resulting from the etching away of Al layer. The best electromagnetic interference properties of − 30 dB within a wide range of frequency with 5.8–26.5 GHz can be achieved in (Ti0.975Fe0.025)3C2Tδ free-standing “paper” made of the corresponding MXene by vacuum-infiltration.

Metamagnetic phase transition of Mn2-xCrxSb (x = 0.07, 0.09, and 0.11) and Mn2-yVySb (y = 0.1, 0.15) alloys had been studied. More Cr and V substitutions lead into increased phase transition temperature, which is confirmed by differential scanning calorimetry (DSC) measurement. The maximized saturation magnetostriction (λs//) of − 1350 ppm and − 610 ppm under 7 T have been realized in Mn1.93Cr0.07Sb alloy and Mn1.9V0.1Sb alloy, respectively, and gradually decreased with more substitution. Giant negative thermal expansion (NTE) is triggered by metamagnetism. The highest linear coefficient of − 42.4 ppm/K is obtained in Mn1.93Cr0.07Sb alloy, but almost zero expansion is obtained in Mn1.85V0.15Sb alloy. The coincident highest ΔSmax associated with the maximized λs// in both Mn2-xCrxSb (x = 0.07, 0.09, and 0.11) and Mn2-yVySb (y = 0.1, 0.15) systems suggests that the strong magnetoelastic coupling is also beneficial to enhance the magnetic entropy change.